Method and Apparatus of Direct Inkjet Offset Lithographic Printing System

Abstract

A method of producing an offset lithographic printing plate including the steps of graining and anodizing an aluminum plate; applying a receptive coating to the grained aluminum; applying an oleophilic inkjet fluid on top of the receptive coating; applying energy to the oleophilic inkjet fluid allowing an oleophilic resin of the oleophilic inkjet fluid to bond with the grained aluminum; and removing a portion of the receptive coating to expose part of the grained aluminum. The step of applying receptive coating can include obtaining a solution having a specific pH range, and maintaining a specific temperature range. A first immersion step is taken to immerse the aluminum plate in the solution, followed by rinsing with a portion of demineralized water. The invention can also include a second immersion step to immerse the aluminum plate in a surfactant water solution.

What is claimed is: 
     
         1 . A method of producing an direct inkjet offset lithographic printing plate, the method comprises steps of:
 graining and anodizing an aluminum plate to create a grained aluminum;   applying a receptive coating to the grained aluminum;   applying an oleophilic inkjet fluid on top of said receptive coating;   applying sufficient energy to said oleophilic inkjet fluid allowing an oleophilic resin of the oleophilic inkjet fluid to bond with said grained aluminum; and   removing a portion of said receptive coating to expose a surface of the grained aluminum.   
     
     
         2 . The method as recited in  claim 1 , wherein the receptive coating on the grained aluminum comprises:
 a mixture of polyethylene glycol from approximately 0.1% to approximately 1%, sodium hydroxide from approximately 0.5% to approximately 1.5%,   a surfactant from approximately 1% to approximately 5%,   a water soluble polymer from approximately 5% to approximately 50%, and sufficient water to make 100%;   wherein the surfactant selected to make a contact angle of 90 degrees or less between a sessile drop of the inkjet fluid and the aluminum plate.   
     
     
         3 . The method as recited in  claim 1 , wherein the oleophilic inkjet fluid comprises:
 approximately 5% to approximately 10% of an aqueous acrylic polymer emulsion formed from one or a plurality of monomers selected from styrene, vinyl acetate, vinyl toluene and acrylic or methacrylic acid esters of alcohols of 1 to 4 carbon atoms and a minor amount of acrylic or methacrylic acid, and approximately 1% to approximately 2% of a 35% solution on ammonia in water, and   approximately 0.1% to approximately 10% surfactant, wherein the surfactant selected to produce a surface tension from approximately 20 to approximately 40 dynes/centimeter to the mixture, and   approximately 5% to approximately 10% of triethanolamine, and   approximately 0.5% to approximately 1.5% dye, and   water to make 100%.   
     
     
         4 . The method as recited in  claim 1 , wherein the viscosity of the injket fluid is between approximately 2 and approximately 10 centipoises. 
     
     
         5 . The method as recited in  claim 1 , wherein the viscosity of the injket fluid is between approximately 4 and approximately 6 centipoises. 
     
     
         6 . The method as recited in  claim 1 , wherein the step of applying receptive coating comprises:
 obtaining a solution having a pH in a range of 11.5 to 11.8;   maintaining a temperature in said solution to 35° C.+/−5%;   a first immersion step to immerse the aluminum plate in the solution;   removing the aluminum plate from the solution after the first immersion step;   rinsing the aluminum plate after said first immersion step with a portion of demineralized water.   a second immersion step to immerse the aluminum plate in a surfactant water solution; and   drying the plate.   
     
     
         7 . The method as recited in  claim 1  further comprising the steps of modifying an interfacial tension on said surface such that said inkjet fluid has a surface tension that is higher than said interfacial tension. 
     
     
         8 . The method as recited in  claim 3  further providing a hydrophilic characteristic of said surface by using the receptive coating where the receptive coating is a water soluble film having a surface tension that is lower than said inkjet fluid. 
     
     
         9 . The method as recited in  claim 2 , wherein the second immersion step takes place within 30 seconds following a completion of the rising step. 
     
     
         10 . The method as recited in  claim 2 , wherein the first immersing step has a dwell time of between 30 to 60 seconds, and wherein the second immersing step has a dwell time of between 30 to 60 seconds. 
     
     
         11 . The method as recited in  claim 2 , wherein the solution has a portion of deionized water and a portion of sodium hydroxide in 1:4 ratio. 
     
     
         12 . The method as recited in  claim 1 , wherein the oleophilic inkjet fluid comprises:
 about 78.17% HPLC grade water;   about 7.72 a polymer of one or a plurality of monomers selected from styrene, vinyl acetate, vinyl toluene and acrylic or methacrylic acid esters of alcohols of one to four carbon atoms and a minor amount of acrylic or methacrylic acid;   about 1.5% ammonia 33%;   about 0.35% diol surfactant Acetylene;   about 0.27% Surfactant Disodium salt of half ester of sulphosuccinic acid in water;   about 3.47% Surfactant nonionic Polyoxyethylene Ether Tridecyl;   about 7.52% Complexing ion Triethanolamine; and   about 0.96% Coloring dye.   
     
     
         13 . The method as recited in  claim 1 , wherein the step of applying energy comprises applying energy to the oleophilic inkjet fluid to a temperature of between 190 to 210° C., with a dwell time of between 4-10 minutes. 
     
     
         14 . A method of improving resolution in direct inkjet offset lithographic printing, the method comprising:
 providing a printer having a grained aluminum as a substrate;   applying a low surface tension coating to the grained aluminum;   applying an high surface tension inkjet fluid on top of said receptive coating to create a desired image area;   applying energy to said inkjet fluid allowing an oleophilic resin of the inkjet fluid to bond with said grained aluminum;   using a dampening system to wash away a portion of said coating to expose a hydrophilic surface of the grained aluminum; and   applying ink to said image area.   
     
     
         15 . The method of direct inkjet offset lithographic printing as recited in  claim 10 , wherein applying receptive coating comprises:
 obtaining a solution having a pH higher than 9;   maintaining a temperature in said solution to 35° C.+/−5%;   a first immersion step to immerse the aluminum plate in the solution;   removing the aluminum plate from the solution after the first immersion step;   rinsing the aluminum plate after said first immersion step with a portion of demineralized water; and   a second immersion step to immerse the aluminum plate in a surfactant water solution.   
     
     
         16 . The method of direct inkjet offset lithographic printing as recited in  claim 11 , wherein the solution has a portion of deionized water and a portion of sodium hydroxide. 
     
     
         17 . A direct inkjet offset lithographic printing system with improved resolution, said system comprising:
 a housing;   an offset plate disposed within the housing;   a print head disposed within the housing to digitally place droplets of inkjet fluid on the plate, where said inkjet fluid has a high surface tension;   a dampening system coupled to the offset plate;   wherein the plate has a hydrophilic surface.   
     
     
         18 . The direct inkjet offset lithographic printing system as recited in  claim 13 , wherein the plate has a coating on the surface of the plate, and the coating has a surface tension that is lower than the surface tension of the inkjet fluid. 
     
     
         19 . The direct inkjet offset lithographic printing system as recited in  claim 14 , further comprising a coating applicator in the housing to apply said coating onto said offset plate. 
     
     
         20 . The direct inkjet offset lithographic printing system as recited in  claim 15 , wherein the dampening system washes at least a portion of the receptive coating off of said offset plate. 
     
     
         21 . The direct inkjet offset lithographic printing system as recited in  claim 16 , further comprising a Far IR energy applicator disposed within said housing to apply energy to said offset plate.